No computer maker, Apple including, escapes from the bad habit of making one pay inflated prices for repairs not covered by the guarantee. It is practically impossible to repair a portable without being invoiced several hundreds of euros, very far from the real cost of the parts and the labour. Thus it is not surprising that many people give up repairing their portable and prefer to repurchase new by adding (a little) money.
However the more courageous handymen launch out on a bit of do-it-yourself which sometimes arrive at very successful reconversions their machines.
One can see this at the site http://wolphbite.com where a MacBook has been transformed into a mini Mac Pro.
Attention, without being too complex, this " mod" nevertheless required delicate use of the soldering iron and a large amount of ingenuity.